The primary function of the Neurophysiology Core will be to perform terminal experiments on animals that have been the subject of long-term behavioral and/or anatomical investigations in the three component subprojects of this Program. The central objective is to obtain electrophysiological data that will complement or extend the interpretation of results derived from studies of spinal cord injury (SCI) and intraspinal transplantation detailed elsewhere in this Project proposal. Thus, emphasis of the electrophysiological studies will be on spontaneous or graft-mediated restoration of specific functional connections and/or the utilization of alternative functional pathways. The Neurophysiology Core will thus provide a critical dimension in our multidisciplinary approach toward studies of SCI and cellular repair. Aside from fiscal considerations, this entity will even more importantly serve to unify this Program by providing a centralized forum for information exchange between subprojects. The Neurophysiology Core will thus be the platform on which a more comprehensive understanding can be obtained of the functional efficacy of cellular intervention in clinically-relevant animal models of SCI. The specific aims of the Core thus reflect directly on component parts of each subproject. These objectives include: (i) to determine if there is evidence for long propriospinal connectivity between hindlimb afferents and forelimb motoneuron pools following injury with or without neural grafts in a cat model for coordinated forelimb-hindlimb locomotion following chronic thoracic spinal cord contusion injury, (ii) to determine if there is evidence for a change in segmental reflex circuitry modulating flexors and extensors of the ankle and whether neural tissue grafts normalize these parameters in a cat model for hindlimb reflexes and bipedal locomotion following chronic thoracic spinal cord contusion injury, (iii) to determine the efficacy of neural grafts on the normalization of reflex modulation parameters of tibial motoneuron reflex discharges in a rat model for hindlimb reflexes following chronic thoracic or lumbar spinal cord contusion injury, (iv) to determine whether there is electrophysiological evidence for synaptic connectivity between graft cells and host respiratory neurons in a rat model for diaphragmatic breathing following cervical lateral hemiresection, and (v) to determine in a rat model of acute and chronic cervical spinal cord contusion injury whether fetal neural grafts have the capacity to ameliorate diaphragm and abdominal muscle function during cough.